I've been trying to figure out whether there was actually a problem or not with the FBI raid on William Jefferson's offices. Certainly the raid on a member of Congress' office was unprecedented. And certainly Republican leaders such as Denny Hastert and John Boehner are up in arms about it, calling it a separation of powers issue. But does that make it illegal? Or, for that matter, wrong?
On the legal front, Orin Kerr says that, seeing as how the FBI got a warrant from a judge, and seeing as how Jefferson had refused to comply with Justice Department subpoenas for documents relating to the bribery investigation, the raid was probably constitutional, despite the Constitution's Speech and Debate clause declaring that members of Congress be exempt from arrest and questioning while in session. (The clause seems to be there precisely to prevent the executive branch from harassing legislators, the sort of thing you see dictatorships around the world doing all the time.)
On the other hand, Mark Kleiman says we really shouldn't be looking forward to a time when the FBI starts policing members of Congress and regulating corruption, especially since the Justice Department seems to be going after things that are nominally legal. Now granted, if Congress has no interest in policing itself, then someone has to do it, but it's not clear that law enforcement organization with a "deserved reputation for playing dirty" is the agency to do it. After all, these sorts of raids are certainly prone to abuse:
In particular, now that the precedent has been established, what's to keep the Bureau from raiding the offices of Congressional Democrats in leak investigations? Finding a judge to sign a search warrant is trivial, especially in any case with the "national security" label.
Maybe that's a pretty outlandish concern, but it's not impossible. And more realistically, what's to stop a vindictive administration from getting the FBI to investigate bribery charges on various Senators and members of Congress for political gain? After all, corruption is a pretty strong accusation, and can certainly damage or weaken a sitting member of Congress, even if it's totally false. That's not to say that Jefferson's innocent or that the FBI is simply being vindictive in this case, but there are definitely issues to worry about.